Single pole snap action dome or oil can switches have been used to provide reliable electrical switch contacts in relatively low-current apparatus, for example electronic calculators or computers. Such switches have typically utilized a dome-shaped switch element to make and break electrical contact with an associated underlying conducting contact. In its stable or rest state, the dome is supported in spaced relation over the underlying contact. When the dome is pressed, it flexes in a snap action fashion so that a portion of the dome, typically the central portion, presses against the underlying contact and thereby establishes an electrical connection. When pressure is removed from the dome, it snaps back to its rest state and therefore disconnects from the underlying contact.
The above-described dome element may be made of a relatively strong conducting material such as stainless steel. The resiliency of the element is achieved by making the conducting material of the dome sufficiently thin to allow the required flexing movement.
A relatively thin, flexible dome is generally not well suited for high current switching applications, because high current tends to heat and therefore damage the dome. In addition, any arcing such as occurs in high current applications will relatively easily cause damage to the dome.
Many switching applications, for example automotive switching applications, require a compact and reliable switch which operates at relatively high currents. Thus, for example, a switch which operates power windows of an automobile must pass relatively high current to run motors that raise and lower the windows. Such switches must operate in a double throw manner to apply power to operate a window motor when the switch is pressed and to apply a ground signal to maintain the motor in a braked condition when the switch is released.
Although a snap action switch having a dome switching element provides a simple and reliable means for switching, it would no doubt be considered unreliable or undesirable in controlling window motors, because snap action dome switches have heretofore been used in a single throw manner and are typically employed in low current applications.
Accordingly, it is an object of the invention to provide a simple and reliable snap action switch which may be utilized for high current switching applications.
A further object of the invention is to provide such a switch which operates in a double throw manner.
Another object of the invention is to provide a double throw snap action dome switch which defines one switch state when the dome is pressed to flex against an underlying contact and defines a second switch state when the dome is released to snap back to a stable position in contact with an overlying conducting plate.
A further object of the invention is to provide a snap action switch with a dome-shaped switching element which includes one or more flexible spring arms that hold the dome in its stable rest state against a grounded conducting plate and that allow the dome to flex downwardly in response to pressure to move from the grounded plate and against an underlying contact.